Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endonucleases from Micrococcus luteus that induce single-strand breaks in gamma-irradiated DNA have been separated chromatographycally into two groups. The first group involves two different enzymes: AP-endonuclease II (mol. weight 30 000) and AP, UV-endonuclease I (mol. weight 15 000) that recognize alkali-labile lesions in gamma-irradiated DNA and apurinic sites in DNA heated at 70 degrees C, pH 6.08 AP-endonuclease II in cooperation with DNA polymerase from M. luteus and T4 phage-induced polynucleotide ligase is capable of carrying out in vitro complete excision repair of alkali-labile lesins in gamma-irradiated DNA. The second group involves gamma-endonucleases X and Y that act on alkalistable gamma-ray lesions. gamma-endonucleases X and Y can be separated by chromatography on DEAE-cellulose but possess similar properties. Activity of gamma-endonucleases toward gamma-irradiated DNA is inhibited by only heavily UV-irradiated DNA (15 000 ergs/mm2). The data are consistent with the hypothesis that gamma-endonucleases are specific for thymine glycols (t' and tUV) in UV- and gamma-irradiated DNA.
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PMID:[Analysis of the activity of Micrococcus luteus endonucleases with respect to gamma-irradiated DNA]. 2 Jan 61

Highly purified preparations of RNA-directed DNA polymerase from avian myeloblastosis virus (AMV) contain a Mn2+-activated endonuclease activity capable of nicking supercoiled DNA. This endonuclease activity co-sediments in glycerol gradients with the alphabeta form of AMV DNA polymerase, and co-chromatographs with DNA polymerase activity on DEAE-cellulose, phosphocellulose, and heparin-Sepharose. It is also present in AMV alphabeta-DNA polymerase purified by electrophoresis through nondenaturing polyacrylamide gels and subsequently chromatographed on poly(C)-agarose. alphabeta-associated endonuclease is co-immunoprecipitated with DNA polymerase activity by antiserum directed against alphabeta holoenzyme. The alpha form of AMV DNA polymerase lacks this activity. In its enzymatic properties, alphabeta-associated endonuclease resembles the endodeoxyribonuclease activity associated with the AMV p32 protein, which has been shown to be structurally related to the beta (but not the alpha) subunit of AMV DNA polymerase.
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PMID:Endonuclease activity of purified RNA-directed DNA polymerase from avian myeloblastosis virus. 8 98

Several lines of research have suggested that the dCMP hydroxymethylase (HMase) coded by bacteriophage T4 is an essential protein in a DNA replication complex, as well as a supplier of hydroxymethyl dCMP for phage DNA synthesis. We show that a mutant [HMase, dCTPase, endonuclease II, endonuclease IV] which lacked this enzyme made cytosine-containing DNA at about two-thirds of the normal rate. When coupled with an alc mutation which permitted synthesis of late proteins, a small burst of phage was produced whose DNA contained no hydroxymethylcytosine. This pentuple mutant made both early and late proteins with abnormal kinetics, whereas the HMase+ parent showed normal kinetics. However, intracellular phage DNA showed no gross abnormalities in alkaline sucrose gradients. We conclude that HMase is not required for DNA synthesis when hydroxymethyl dCMP is not needed as a substrate; however, its absence still impairs both replication and transcription.
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PMID:Synthesis of T4 DNA and bacteriophage in the absence of dCMP hydroxymethylase. 21 5

The main endonuclease for apurinic sites of Escherichia coli (endonuclease VI) has no action on normal strands, either in double-stranded or single-stranded DNA, or on alkylated sites. The enzyme has an optimum pH at 8.5, is inhibited by EDTA and needs Mg2+ for its activity; it has a half-life of 7 min at 40 degrees C. A purified preparation of endonuclease VI, free of endonuclease II activity, contained exonuclease III; the two activities (endonuclease VI and exonuclease III) copurified and were inactivated with the same half-lives at 40 degrees C. Endonuclease VI cuts the DNA strands on the 5' side of the apurinic sites giving a 3'-OH and a 5'-phosphate, and exonuclease III, working afterwards, leaves the apurinic site in the DNA molecule; this apurinic site can subsequently be removed by DNA polymerase I. The details of the excision of apurinic sites in vitro from DNA by endonuclease VI/exonuclease III, DNA polymerase I and ligase, are described; it is suggested that exonuclease III works as an antiligase to facilitate the DNA repair.
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PMID:Properties of the main endonuclease specific for apurinic sites of Escherichia coli (endonuclease VI). Mechanism of apurinic site excision from DNA. 34 34

An endodeoxyribonuclease has been purified 750-fold from human KB cells. The purified endonuclease requires Mg2+ for maximum activity: Mn2+ was less than half as active and Ca2+ inhibited the reaction. The optimum pH is 8.8 in Tris-HCl and the optimum buffer concentration is 10 mM. KCl (and NaCl), --SH-reacting reagents, and tRNA strongly inhibit the reaction. An apparent molecular weight of 54,000 was determined by sedimentation in a glycerol gradient. The purified endonuclease cleaved native, double-stranded adenovirus 2 DNA, and the reaction proceeded stepwise during the initial stage of degradation by cleavage of the DNA substrate in half, then in half again, etc. At longer digestion times, single strand scissions were detected. RNA was not a substrate for the enzyme. Poly(dG) . poly(dC) was susceptible but poly(dA) . poly(dT) was resistant to degradation. Hydrolysis of adenovirus 2 DNA yielded double-stranded polynucleotides containing 5'-phosphoryl and 3'-hydroxyl termini with short, single-stranded regions presumably at the ends. More than 50% of the product of a limit digest had a chain length greater than 35 to 40 nucleotides. Analysis of the 5' and 3' end groups of the digestion products indicated a preference for the site of the enzymatic cleavage; thymidylic acid residues were present at the 5' end and deoxyguanosine residues at the 3' end, each with a frequency of 40 to 50%.
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PMID:An endodeoxyribonuclease of human KB cells. Purification and properties of the enzyme. 64 80

An endonuclease of Escherichia coli active on a DNA treated with methylmethane sulfonate has been separated from an endonuclease active on depurinated sites. The former enzyme is disignated here as endonuclease II, while the latter enzyme is designated as apurinic acid endonuclease. Endonuclease II is also active on DNA treated with methylnitrosourea, 7-bromomethyl-12-methylbenz[a]anthracene, and gamma-irradiation. A third fraction which contains activities for both depurinated and alkylated sites needs further study. Endonuclease II, molecular weight 33,000, has been purified 12,500-fold and does not have exonuclease III activity. Apurinic acid endonuclease, molecular weight 31,500, has been purified 11,000-fold and does not have exonuclease III activity. Exonuclease III, molecular weight 26,000, has been purified 2300-fold and does not have endonucleolytic activity at depurinated reduced sites or at alkylated sites in DNA. Therefore, these are three separate proteins. Exonuclease III can produce, presumably by its exonucleolytic activity, double-strand breaks in heavily alkylated DNA under conditions where it does not make single-strand endonucleolytic breaks at either depurinated-reduced or alkylated sites.
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PMID:Endonuclease II, apurinic acid endonuclease, and exonuclease III. 79 74

An endonuclease (AP-endonuclease II) that specifically attacks double stranded or single stranded depurinated DNA, resulting in single-strand nicks, has been purified 320-fold from Micrococcus luteus. The enzyme is not stimulated by 0.002 M MgCl2, it induces 3'OH-5'PO4 breaks on the 5' side of apurinic sites, it has no activity towards UV-irradiated DNA and has a molecular weight of about 30 000. In cooperation with DNA-polymerase from M. luteus and T4 DNA ligase, AP-endonuclease II has been shown capable of carrying out complete excision repair of depurinated DNA in vitro.
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PMID:[Isolation and properties of Micrococcus luteus endonucleas acting in DNA depurinization but inactive with pyrimidine dimers]. 88 77

Escherichia coli cells infected with T4 phage which are deficient in both nuclear disruption and endonuclease II exhibit a pathway of host DNA degradation which does not occur in cells infected with phage deficient only in endonuclease II. This alternate pathway of host DNA degradation requires T4 endonuclease IV.
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PMID:Host DNA degradation after infection of Escherichia coli with bacteriophage T4: dependence of the alternate pathway of degradation which occurs in the absence of both T4 endonuclease II and nuclear disruption on T4 endonuclease IV. 108 2

An enconuclease activity that reacts with x-irradiated DNA is present in extracts of E. coli. By using centrifugal methods to monitor the conversion of the supercoiled, circular double-stranded DNA for phage phi-x-174 (replicative form) or PM2 to the relaxed circular form it was possible to quantitate the rate of radiation induced endonuclease-sensitive sites in the DNA. For every single-strand break induced by x-rays under aerobic irradiation conditions, there is approximately one induced site sensitive to this endonuclease activity. Under irradiation conditions (addition OF Potassium iodide) that dramatically reduce rates of single-strand breaks and "alkalilabile" lesions, the number of endonuclease-sensitive sites relative to single-strand breaks increase approximatley 4-fold. This nuclease is present in several strains of E. coli B and K12, including mutants deficient in DNA polymerase I, recombination gene products (rec mutants), ultraviolet light incision enzyme (uvr A mutant), and endonuclease II. It is suggested that this endonuclease may be involved in an excision repair process for damages incurred in DNA by ionizing radiation.
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PMID:Endonucleolytic incision of x-irradiated deoxyribonucleic acid by extracts of Escherichia coli. 109 50

The endonuclease specific for apurinic sites in DNA has been isolated from Escherichia coli B41 as a pure monomeric protein of 32,000 daltons. The enzyme hydrolyzes a phosphodiester bond near the apurinic sites in double-stranded DNA; it does not hydrolyze untreated DNA and its action on alkylated DNA is restricted to the apurinic sites always present. This enzyme is not endonuclease II which is most probably a mixture of two enzymes, one a glycosidase (Kirtikar, D. M., and Goldthwait, D. A. (1974) Proc. Natl. Acad. Sci. U. S. A. 71, 2022-2026), the other an endonuclease for apurinic sites which is the enzyme isolated in this work.
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PMID:Purification of Escherichia coli endonuclease specific for apurinic sites in DNA. 110 Jun 31


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